Apparatus for injecting fresh air into outboard motor underwater exhaust



Sept. 9, 1969 5. J. GWIDT 3,465,706

APPARATUS FOR INJECTING FRESH AIR INTO OUTBOARD MOTOR UNDERWATER EXHAUST Filed Feb. 5, 1968 Sieve J. Gwidf INVENTOR.

United States Patent ()1 fice 3,465,706 Patented Sept. 9, 1969 3,465,706 APPARATUS FOR INJECTING FRESH AIR INTO OUTBOARD MOTOR UNDERWATER EXHAUST Steve J. Gwidt, P.O. Box 327, Rhinelander, Wis. 54501 Filed Feb. 5, 1968, Ser. No. 702,933 Int. Cl. B63h 21/26 U.S. Cl. 11517 7 Claims ABSTRACT OF THE DISCLOSURE An addition to an outboard drive unit of the type including an upstanding leg in whose lower portion a horizontal propeller shaft is journaled having a propeller thereon and which also includes an underwater exhaust outlet disposed in the area of the propeller but rearwardly thereof and at a point spaced laterally of the axis of rotation of the propeller, the addition including means whereby air under atmospheric pressure is supplied to the area disposed immediately behind the propeller and in alignment with its axis of rotation and thus may be discharged into the ambient water in order to aerate the same, dilute the exhaust gases being discharged from the exhaust gas outlet and buoy up the exhaust gas contaminants for dispersal into the ambient atmosphere above the water.

Most outboard drive units of the type including an upstanding leg in whose lower end a horizontal propeller shaft is journaled having a propeller thereon also include an exhaust gas outlet disposed to the rear of the propeller and spaced at least slightly above the axis of rotation of the propeller. When an outboard drive unit of this type is operated considerable quantities of exhaust gases are discharged from the outboard drive unit directly into the water in the area of the propeller wash. This exhaust gas is quickly broken up into small pockets and at least to some degree washed by the propeller wash with the result that most all contaminants such as unburned particles of hydrocarbon fuel, lubrcating oil and carbon particles remain in the water and contaminate the same.

The main object of this invention is to provide a means for diluting the exhaust gases discharged from the outboard drive unit with large quantities of air from the ambient atmosphere closely adjacent the exhaust gas outlet.

Another object of this invention, in accordance with the immediately preceding object, is to provide means whereby fresh air from the ambient atmosphere and under atmospheric pressure may be directly communicated with the underwater area disposed immediately rearwardly of and in axial alignment with the propeller of an outboard drive unit whereby the reduced pressure area immediately behind the propeller when the latter is spinning and the outboard drive unit is moving through the water at reasonable speed will cause large quantities of air from the ambient atmosphere to be drawn into the area disposed immediately behind and in axial alignment with the propeller.

A further object of this invention, in accordance with the immediately preceding object, is to provide a diffuser ically feasible, long lasting and relatively trouble-free in operation.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a fragmentary longitudinal vertical sectional view of the rear end of a boat having a conventional outboard motor mounted on the transom of the boat and with the apparatus of the instant invention incorporated in the outboard motor;

FIGURE 2 is an enlarged fragmentary longitudinal vertical sectional view taken substantially upon a plane passing through the center of the lower portion of the upstanding leg of the outboard motor illustrating the manner in which the apparatus of the instant invention may be incorporated in an otherwise substantially conventional outboard motor lower unit;

FIGURE 3 is an enlarged sectional view taken substantially upon a plane indicated by the section line 33 of FIGURE 2; and

FIGURE 4 is a perspective view of the tubular shaft and integral air diffusing portions of the instant invention.

Referring now more specifically to the drawings, the numeral 10 generally designates a small fishing boat or the like including opposite sides 12 interconnected by a bottom wall 14 and a rear upstanding transom 16. A generally conventional outboard motor referred to by the reference numeral 18 is mounted on the transom 16 in the usual manner by means of a clamp bracket 20 and the outboard motor 18 includes the usual depending leg 22 in which there is disposed a journaled drive shaft 24 extending downwardly toward the lower unit referred to in general by the reference numeral 26 and secured to the lower end of the leg 22.

The lower unit 26 includes a bearing assembly 28 for the lower end of the drive shaft 24 and a bevel gear 30 is mounted on the lower end of the drive shaft 24 and meshed with a bevel gear 32 carried by a tubular propeller shaft 34 journaled through the lower unit 26 by means of front and rear bearing assemblies 36 and 38.

The rear end portion of the propeller shaft 34 projects rearwardly of the lower unit 26 and has a conventional marine propeller 40 mounted thereon for rotation therewith. The tubular propeller shaft also extends rearwardly of the propeller 40 and opens into a difiuser assembly referred to in general by the reference numeral 42 to be hereinafter more specifically described.

The front end of the propeller shaft 34 opens forwardly out of the forward end of the lower unit 26 and is in direct fluid-tight sealed communication with the rearwardly opening lower end of an upstanding fresh air tube 46. The fresh air tube 46 is supported from the leg 22 by means of a pair of U-bolts 48 whose free ends are secured through opposite side apertured mounting lugs 50 carried by the leg 22 by means of fasteners 52 and the fresh air tube 46 is of a length to project upwardly to a point considerably above the surface 54 of the water 56 in which the boat 10 is disposed. The upper end of the fresh air tube 46 may be flared as at 58 and in this manner fresh air from the atmosphere above the surface 54 may enter the upper end of the fresh air tube 46, pass downwardly through the tube 46 and be discharged from the lower end of the tube 46 directly into the forward end of the propeller shaft 34.

The diffuser assembly 42 includes a pair of U-shaped and crossed diffuser blade defining plates 62 having leg portions 66 between whose free ends the rear end of shaft 34 is received and secured in any convenient man-' ner such as by welding 68 and a round disk 70 is secured to the crossed bight portions 72 of the plates 62. Thus,

the crossed plates 62 define generally radially extending blades which, when the shaft is spinning rapidly, create considerable vacuum rearward of the propeller 40 in order to draw large quantities of air through the tube 46 for discharge immediately adjacent the exhaust outlet 76 of the lower unit 26 so as to drive the exhaust gases out of the water and aerate the latter. In addition, the plates 62 insure that the fresh air discharged rearward of the propeller 40 from the propeller shaft 34 is forced radially outwardly toward the rearwardly and downwardly opening exhaust outlet 76 of the lower unit 26.

Although the diffuser assembly is provided in order to define a centrifugal blower-type attachment for further reducing the pressure in the area immediately rearwardly of the rear end of the propeller shaft 34 and thus to draw greater quantities of fresh air from the ambient atmosphere down into the fresh air tube 46, the diffuser assembly 42 is not required in order to provide ample air flow from the rear end of the propeller shaft 34 inasmuch as a reduced pressure area is formed immediately rearwardly of the marine propeller 40 independent of the diffuser assembly 42. Actually, although the diffuser assembly 42 functions to increase the air discharge from the rear end of the propeller shaft 34, it also functions to insure that at least a portion of the air being discharged from the rear end of the propeller shaft 34 is directed radially outwardly toward the exhaust gas outlet 76.

It is presently well known that the exhaust gases themselves may be discharged rearwardly through a hollow propeller hub without adversely affecting the performance of the propeller. Accordingly, the rearward discharge of fresh air from the rear end of the propeller shaft 34 will have no adverse effect on the operation of the propeller 40. The main reason for discharging fresh air rearwardly from the rear end of the propeller shaft 34 is to provide a means whereby the exhaust gases being discharged from the exhaust gas outlet 76 may be diluted and more quickly buoyed up to the surface 54 of the water 56 for commingling with the atmosphere above the surface 54 as opposed to the exhaust gases being washed by the turbulence of the prop wash and thus contaminating the water.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

I claim:

1. In combination, a support, a propeller shaft journalled from said support and adapted to be disposed in water to be aerated, one end portion of said shaft being hollow and having a marine propeller mounted thereon, said hollow end portion opening rearwardly through said propeller, air conduit means including an elevated end adapted to extend upwardly to a level above the water level in which the shaft is disposed, the upper end of said air conduit means being open and adapted for communication with the ambient atmosphere, the other end of said air conduit means being in reasonably good sealed communication with the hollow rear end portion of said shaft, and a diffuser assembly carried by the rear end portion of said propeller shaft into whose center area air from said propeller shaft is discharged, said diffuser assembly including generally radially extending blade portions for directing said air radially outwardly of the axis of rotation of said propeller shaft.

2. In combination with an outboard drive unit of the type including an upstanding leg in whose lower end a horizontal propeller shaft is journaled, the rear end portion of said shaft projecting horizontally outwardly of the lower end portion of said leg and having a marine propeller mounted thereon, said propeller shaft including a hollow rear end portion opening through said propeller, air conduit means extending upwardly from the lower end portion of said leg to a level above the normal water level on said leg, the upper end of said air conduit means being open and adapted for communication with the ambient atmosphere, the lower end of said air conduit means being in reasonably good sealed communication with the hollow rear end portion of said shaft, said leg including exhaust gas passage means opening outwardly of said leg below said water level adjacent the area in which said propeller and rear end of said propeller shaft are disposed, a diffuser assembly carried by the rear end portion of said propeller shaft into whose center area air from said propeller shaft is discharged, said diffuser assembly including generally radially extending blade portions for directing said air radially outwardly of the axis of rotation of said propeller shaft.

3. In combination with an outboard drive unit of the type including an upstanding leg in whose lower end a horizontal propeller shaft is journaled, the rear end portion of said shaft projecting horizontally outwardly of the lower end portion of said leg and having a marine propeller mounted thereon, said propeller shaft including a hollow rear end portion opening through said propeller, air conduit means extending upwardly from the lower end portion of said leg to a level above the normal water level on said leg, the upper end of said air conduit means being open and adapted for communication with the ambient atmosphere, the lower end of said air conduit means being in reasonably good sealed communication with the hollow rear end portion of said shaft, said leg including exhaust gas passage means opening outwardly of said leg below said water level adjacent the area in which said propeller and rear end of said propeller shaft are disposed, said propeller shaft being tubular and opens outwardly of its forward end through the front wall portion of said leg, said air conduit means comprising an upstanding tube exteriorly mounted on the front wall portion of said leg and opening generally horizontally rearwardly at its lower outlet end into the forward inlet end of said tubular propeller shaft.

4. The combination of claim 3 including a diffuser assembly carried by the rear end portion of said propeller shaft into whose center area air from said propeller shaft is discharged, said diffuser assembly including generally radially extending blade portions for directing said air radially outwardly of the axis of rotation of said propeller s a t.

5. In combination with an outboard drive unit of the type including an upstanding leg in whose lower end a horizontal propeller shaft is journaled, the rear end portion of said shaft projecting horizontally outwardly of the lower end portion of said leg and having a marine propeller mounted thereon, said propeller shaft including a hollow rear end portion opening through said propeller, air conduit means extending upwardly from the lower end portion of said leg to a level above the normal water level on said leg, the upper end of said air conduit means being open and adapted for communication with the ambient atmosphere, the lower end of said air conduit -means being in reasonably good sealed communication with the hollow rear end portion of said shaft, said leg including exhaust gas passage means opening outwardly of said leg below said water level adjacent the area in which said propeller and rear end of said propeller shaft are disposed, said upstanding leg comprising the leg portion of an outboard motor including a mounting clamp from which said leg is supported for steering oscillation about an upstanding axis and oscillation about a horizontal axis extending transversely of said outboard motor, said propeller shaft being tubular and opens outwardly of its forward end through the front wall portion of said leg, said air conduit means comprising an upstanding tube exteriorly mounted on the front wall portion of said leg and opening generally horizontally rearwardly at its lower outlet end into the forward inlet end of said tubular propeller shaft.

6. In combination, depending outboard drive unit leg from whose lower end a marine propeller is journaled, said leg including exhaust gas passage means therein opening outwardly at the outlet end thereof in the area of said propeller but rearwardly thereof and at a point spaced laterally of the axis of rotation of said propeller, and fresh air passage means including an inlet end portion above the normal operative water level of said leg and an outlet end portion extending through said propeller and opening outwardly rearward of the plane in which the blades of said propeller swing, said fresh air passage means including a tubular propeller shaft upon which said propeller is mounted arid which is journaled from the lower end of said drive unit leg, the rear end of said shaft comprising the outlet end of said fresh air passage means.

References Cited UNITED STATES PATENTS 3,045,423 7/1962 Hulsebus l1517 XR 3,109,495 11/1963 Lang.

FOREIGN PATENTS 776,656 11/1934 France.

ANDREW H. FARRELL, Primary Examiner 

